Manufacture of sound ingots and billets of special steel



{D zine-ore j serene.

AND IBILLETS Bl? ESflPECIALfi'ITEEL.

llpeclfication OJ.

No Drawing. application filed Il /Kay 531,

1 0 all 207mm xix" may cone/1m Be it known that l, liir ltoinnrr iluseoir'r l laormno, lmrouct, F. ii. if, a subject of the King of (treat Britain and Ilrelaiul, residing at the city of ll estminstcr, llugland, have invented improvements in or Relating to the lrlanufacture of Sound lngots and Billets of Special of which the following a specification.

This invention has reference to the manufacture of soundv ingots and billets of special steel, particularly suitable for use in aeroplanes and motor Construction.

in the manufacture of steel billets for use in aeroplane construction, it has heretoforebeen usual to make the steel in a large open hearth furnace and cast it into ingots of large size and section, say of the order of about sixteen inches square and inward, and to reduce the ingot into a round bloom or bar, by hammering or rolling, preparatory to converting it into billets for use in the construction of parts of aeroplanes.

As it is very essential that billets for the purpose mentioned shall be as free as possible from defects, and as there is a liability of a steel ingot made as described being sometimes defective, it has heretofore been considered necessary, that, after reducing the ingot into a round or square bloom, billet or bar by hammering, cogging, or rolling, such cogged or otherwise Worked bloom, billet or bar, should, before being converted into finished billets for aeroplane or other Work, be machined, that is to say turned or planed, in order to remove defects therein before proceeding to convert it into lin ished billets. T his involves not'only the cost of machining, but also the cooling of the bloom, billet or bar before machining it, and the reheating of the machined bloom, billet or bar preparatory to reducing it, by further rolling, into a form suitable for conversion into finished billets. This practics of cogging large ingot into a round or square bloom or bar, cooling the bloom or bar, machining oil the surface thereof and reheating for conversion into linished billets, is a, very expensive one, takes considerable time and the yield of finished billets is low, probably not more than about of the original ingot being in most cases obtained as finished billets.

lh OXV the present invention has reference to the manufacture of sound ingots of speclal steel of such a high degree oi: soundness ltcttcrs Patent Patented Feb. 8, 1921.

1919. Serial no. 298.7%.

and freedom from defects, that they can safely be converted into fimshed billets suitable tor use 111 the construction of parts of aeroplanes and for other Work. without any necessity for machining the blooms or bars made therefrom, for the purpose hereinbefore set forth, preparatory to their conversion into finished billets, thereby facilitating "apid production of finished billets, cheapening the manufacture of such billets and effecting agreat saving in steel inasmuch as with sound ingots made of special steel according to the present invention, a yield of billets approximating 80% of the original ingot can be obtained.

In the manufacture of sound ingots and billets of special steel according to'the pres ent invention and particularly suitable for the purpose set forth, the steel base for the material to be produced, may be ordinary carbon steel turning-s or scrap, or both, or alloy steel, which may advantageously be nickel-chromiuni steel turnings or scrap, or both, With, it may be, suitable additions of nickel and chromium, say in the form of fcrro-niclrcl and ferro-chrome. The base material is melted and refined in a furnace of comparatively small capacity, preferably of the order of from about three to six tons capacity, as better results are usually obtained with a furnace of this capacity than with a furnace of larger capacity, such as eight to ten tons and upward capacity.

The melting and refining process is carried out on a basic hearth. the metal charge being first treated to eliminate, as far as necessary, phosphorus, which passes into the slag which is removed after this, the first stage of the process, is finished. For the second stage, there is added to the bath of metal a new slag suitable for the removal of sulfur and oxygen therefrom, and the elimination of these elements is effected in the usual Way. The melting and refining of the steel is effected preferably in an electric furnace. The purified steel is then cast into taper shaped ingots of comparatively small size, say of the order of about nine inches square, and of a height of the order of about three and a half feet, with the large end of the ingot preferably at the top, in a mold having a suitable non-conducting refractory head in order to maintain the upper portion of the metal in a molten condition While the lower portion thereof is cooling and solidifying, so as to insure freedom from piping, segregation and so forth. To assist in obtaining a sound ingot the top of the ingot may be specially heated in known ways. The sound ingot of special steel thus produced is reduced by cogging into a bloom or bar which is afterward reduced by further rolling into a bar or rod of a size suitable for finished billets which are produced by cutting the bar or rod into suitable lengths.

In order to assist in preventing hair cracks or other defects in the steel, care should be taken to avoid using too high 'a casting temperature and to insure that the ingot at no'stagc of the process of its being cast or converted into a billet shall be subjected to any sudden or uneven chilling, or to any sudden increase of temperature from the cold state.

Satisfactory results have been obtained by casting special alloy steel, melted and refined as described, and containing about 30% of carbon, about .15 to 25% .of silicon, about .6076 of manganese, about 70% of chromium, and about 3.50% nickel, in 9 inch square ingot molds, each warm from a previous casting operation and which had been scrubbed, as by a wire brush, to remove adhering foreign matter, then coated with a film of coal tar free from water and provided with a refractory feeder head made of material that is a bad conductor of heat, as

for example a mixture of firebrick, sand and clay, rammed into place, thoroughly dried,

and jointed on the warm ingot mold by means of a quick drying mold facing sand, the height of the feeder head being about ltY/ of that of the ingot mold. About three tons of the steel were poured into a bottom run ladle provided with a fire clay nozzle of about 1-1- inch diameter, the steel being run at a suitable temperature, that is to say, the steel was allowed to stand in the ladle nine or ten minutes before casting into the mold, and was cast at such a temperature that about 2 cwt. of steel was left in the ladle at the end of the casting operation. In other words. the steel was cast as cool as possible compatible with avoidance of an excessive weight of metal being left in the ladle from sculling action. Directly the mold was filled with fnolten steel, the steel was'covered' with powdered slag which quickly became molten. The slag was then covered with charcoal. In order to generate suflicient heat to assist in maintaining the metal in the upper end of the ingot in a molten condition while that in the lower and remaining portion of-the ingot is solidifying, a low pressure air blast may advantageously be applied to the ignited. charcoal to cause its combustion. The ingot was stripped about one hour after casting. and cooled in the open air. The sound ingot of special steel memes thus produced was afterward annealed, reheated to a suitable rolling temperature and reduced by cogging into a bloom or bar, which, without reheating, was converted by further rolling, into a bar of the desired section and cut into lengths to form the required finished sound billets. The bloom or bar may, if desired, be annealed before further rolling it to shape.

In this way, sound ingots and billets of special steel practically free from external and internal defects and particularly suitable for use in the construction of parts of aeroplanes, and motors, for instance crank shafts, though suitable also for other work,

can be produced in a quick and economical manner.

hat I claim is 1. The method of manufacturing sound ingots of special steel such as herein set forth and suitable for the purposes mentioned, said method consisting in melting a comparatively small ahargc of a steel base of the kind herein referred to under basic conditions, refining the molten charge to eliminate phosphorus. sulfur and oxygen therefrom as set forth, removing the purified steel from the refining zone and allowing it to cool for asutlicient time to admit of its being cast as cool as possible compatible with the avoidance of undue sculling action, casting the refined and partially cooled steel into ingots of comparatively small size as set forth and maintaining the upper portion of the metal in each ingot in a molten condition while the lower portion of the metal is cooling and solidifying, substantially as de scribed. V

2. The herein described method of manufacturing sound ingots of special steel such as herein set forth and suitable for the'purposes mentioned, said method consisting in melting a steel base of the kind herein referred to in a basic furnace of comparatively small capacity as set forth, refining the metal charge to eliminate phosphorus, sulfur and oxygen as set forth. then removing the refined steel into a bottom run ladle and allowing it to remain therein. for a suflicient time to admit of its being cast as cool as possible compatible with the avoidance of an excessive weight of metal being left in the ladle from sculling action. then casting the refined and cooled steel into taper shaped ingot molds of comparhtively small size as set forth. with the larger end of-cach mold at the top. and maintaining the upper porion of the ingot in a molten condition while'the lower portion of the ingot is cool ing and solidifying. substantially as de scribed.

Signed at London. England, this second day of Itlay. 1919.

ROBERT ABBOTT HADFIELD. 

